Continental Extension in the western Woodlark Basin: P-T-t-D constraints from Normanby and Misima Islands

巴布亚新几内亚东南部的伍德拉克盆地是世界上延伸最快的裂谷之一，为研究大陆岩石圈在裂谷向海底扩张过渡期间如何破裂提供了天然实验室。 正是在这里，首次发现了D 'Entrecasteaux群岛的活动变质核杂岩（例如，Hill等人，1992年）。这些岛屿保留了地球上已知的一些最年轻、最迅速挖出的变质岩和火成岩（鲍德温等人，1993).挖掘出的D 'Entrecasteaux岛变质核杂岩的下部板块提供了与Woodlark Basin海底扩张系统向西传播同步的活跃大陆伸展和岩浆活动的记录。虽然海底扩张历史（例如，泰勒等人，1999年）和莫尔兹比海山（泰勒和胡雄，在审查）附近的裂谷扩张的过渡是已知的，需要更多的陆上地质研究，以充分了解在伍德拉克盆地大陆裂谷的历史和机制。 大陆岩石圈的破裂提供了事件的热记录，这些事件以矿物中同位素变化的形式保存下来。这些事件可以用热年代学来揭示，当与P-T-D约束相结合时，可以用来确定与大陆伸展和岩浆活动有关的折返时间和速率。 PI建议通过以下方式进一步研究伍德拉克盆地西部大陆裂谷作用与海底扩张之间的关系：1）记录诺曼比岛（D 'Entrecasteaux群岛最东端，位于活动裂谷尖端以西）上出露岩石的P-T-t-D历史; 2）记录米西马岛上出露岩石的P-T-t-D历史;南部裂谷大陆边缘的一部分; 3）确定了D 'Entrecasteaux群岛核杂岩下板块的榴辉岩相变质作用的年龄。 将把结果与以前关于D 'Entrecasteaux群岛和Moresby海山的P-T-t-D研究进行比较。 大陆伸展和岩浆活动的时间的纵向和横向变化（或缺乏）将解释在伍德拉克盆地的海底扩张的历史和最近提出的该地区的演变模型。

The Woodlark Basin of southeastern Papua New Guinea is one of the world's most rapidly extending rifts and provides a natural laboratory to study how continental lithosphere ruptures during the transition from rifting to seafloor spreading. It is here that the active metamorphic core complexes of the D'Entrecasteaux Islands were first discovered (e.g.,Hill et al.,1992). These islands preserve some of the youngest, most rapidly exhumed metamorphic and igneous rocks known on Earth (Baldwin et al.,1993).The exhumed lower plates of the D'Entrecasteaux Island metamorphic core complexes provide a record of active continental extension and magmatism synchronous with the westward propagation of the Woodlark Basinseafloor spreading system. While the seafloor spreading history (e.g.,Taylor et al.,1999) and the transition from rifting to spreading in the vicinity of the Moresby Seamount (Taylor and Huchon, in review) is known, more onshore geologic research is required to fully understand the history and mechanisms of continental rifting in the Woodlark Basin. Rupturing of continental lithosphere imparts a thermal record of events that are preserved as isotopic variations within minerals. These events can be revealed using thermochronology, and when integrated with P-T-D constraints, can be used to determine the timing and rates of exhumation associated with continental extension and magmatism. The PI's propose to further investigate the relationship between continental rifting and seafloor spreading in the western Woodlark Basin by 1) documenting the P-T-t-D histories of rocks exposed on Normanby Island, the easternmost of the D'Entrecasteaux Islands, located west of the active rift tip, 2) documenting the P-T-t-D histories of rocks exposed on Misima Island, part of the southern rifted continental margin and 3) determining the age of eclogite facies metamorphism in the exhumed lower plates of the D'Entrecasteaux Islands core complexes. Results will be compared to previous P-T-t-D studies on the D'Entrecasteaux Islands and Moresby Seamount. Longitudinal and latitudinal variations (or lack thereof) in the timing of continental extension and magmatism will be interpreted in relation to the history of seafloor spreading in the Woodlark Basin and recently proposed models for the evolution of the region.